Chemical mechanical polishing apparatus and method

ABSTRACT

A method includes placing a polisher head on platen, the polisher head including a set of first magnets, and controlling a set of second magnets to rotate the polisher head on the platen, wherein controlling the set of second magnets includes reversing the polarity of at least one second magnet of the set of second magnets to produce a magnetic force on at least one first magnet of the set of first magnets, wherein the set of second magnets are external to the polisher head.

BACKGROUND

Generally, semiconductor devices comprise active components, such astransistors, formed on a substrate. Any number of interconnect layersmay be formed over the substrate connecting the active components toeach other and to outside devices. The interconnect layers are typicallymade of low-k dielectric materials comprising metallic trenches/vias.

As the layers of a device are formed, it is sometimes desirable toplanarize the device. For example, the formation of metallic features inthe substrate or in a metal layer may cause uneven topography. Thisuneven topography creates difficulties in the formation of subsequentlayers. For example, uneven topography may interfere with thephotolithographic process used to form various features in a device. Itis, therefore, desirable to planarize the surface of the device aftervarious features or layers are formed. One method of planarization ischemical mechanical polishing (CMP).

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a perspective view of a CMP apparatus in accordancewith some embodiments.

FIG. 2 illustrates a top view of a CMP apparatus in accordance with someembodiments.

FIGS. 3A-B illustrate side views of a CMP apparatus in accordance withsome embodiments.

FIG. 4 illustrates components of a CMP apparatus in accordance with someembodiments.

FIGS. 5A-B illustrate top views of a CMP apparatus in accordance withsome embodiments.

FIG. 6 illustrates a side view of a CMP apparatus in accordance withsome embodiments.

FIG. 7 illustrates a magnetic base of a polisher head in accordance withsome embodiments.

FIG. 8 illustrates a top view of a CMP apparatus in accordance with someembodiments.

FIG. 9 illustrates a flow chart of a CMP process, in accordance withsome embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Various embodiments are described with respect to a specific context,namely a chemical mechanical polishing (CMP) apparatus and a method ofpolishing a semiconductor wafer using the CMP apparatus. Variousembodiments include using magnets within a polisher head and statormagnets to move the polisher head during a CMP process. The statormagnets may be located, for example, within the platen or external tothe platen. The polarity and strength of the stator magnets may becontrolled to rotate the polisher head. By using magnetic interaction tomove the polisher head, polishing uniformity may be improved.Additionally, maintenance cost of a CMP apparatus may be reduced.

FIGS. 1 through 3A-3B illustrate views of a CMP device 100 in accordancewith some embodiments. FIG. 1 illustrates a perspective view, FIG. 2illustrates a plan view, and FIGS. 3A-3B illustrate a side view. Theillustrations shown in FIGS. 1 through FIGS. 3A-3B are also reflectedschematically in the process flow 400 shown in FIG. 9.

In some embodiments, the CMP device 100 includes a platen 101 over whicha polishing pad 103 has been placed. In some embodiments, the polishingpad 103 may be a single layer or a composite layer of materials such asfelts, polymer impregnated felts, microporous polymers films,microporous synthetic leathers, filled polymer films, unfilled texturedpolymer films, or the like. The polymers may include polyurethane,polyolefins, or the like.

In some embodiments, a polisher head 105 is placed over the polishingpad 103. The polisher head 105 includes a carrier 107, a magnetic base110, and a suction cup 108. The carrier 107 includes one or more catchholes 106 to facilitate placing of the polisher head 105 by a holder150, described in greater detail below in FIGS. 3A-B. During a CMPprocess, a wafer 109 is attached to the polisher head 105 using thesuction cup 108. The respective step is illustrated as step 402 in theprocess flow 400 shown in FIG. 9. The suction cup 108 may be, forexample, a flexible membrane that uses a pressure differential tosecurely hold the wafer 109. The suction cup 108 may be used by, forexample, generating a pressure differential by pressing the wafer 109and the suction cup 108 together to expel air from the volume enclosedby the wafer and the suction cup 108. In some embodiments, an adhesive(e.g., a glue or the like) may be used instead of the suction cup 108 orin addition to the suction cup 108 to attach the wafer 109 to thepolisher head 105. The wafer 109 is positioned so that the surface to bepolished faces downward towards the polishing pad 103. The magnetic base110 of the polisher head 105 includes multiple magnets 120 that areconfigured to interact with stator magnets (e.g., stators 130 or stators330, described below in FIGS. 4 and 6, respectively) in order to apply adownward force or pressure on the wafer 109 when the wafer 109 is incontact with the polishing pad 103. The magnetic base 110 is alsoconfigured to interact with stator magnets to translate or rotate thepolisher head 105 during a CMP process. In some embodiments, thepolisher head 105 is freestanding (e.g., not mechanically attached toanother component) during a CMP process.

In some embodiments, the CMP apparatus 100 includes a slurry dispenser111, which is configured to deposit a slurry 113 onto the polishing pad103. In some embodiments, the platen 101 is configured to rotate, whichcan cause the slurry 113 to be distributed between the wafer 109 and thepolishing pad 103. In some embodiments, the platen 101 remains fixedduring a CMP process. The composition of the slurry 113 depends on atype of material to be polished. For example, the slurry may comprise areactant, an abrasive, a surfactant, and/or a solvent. The reactant maybe a chemical, such as an oxidizer or a hydrolyzer, which willchemically react with a material of the wafer 109 in order to assist thepolishing pad 103 in grinding away the material. In some embodiments inwhich the material is tungsten, the reactant may be hydrogen peroxide,although any other suitable reactant, such as hydroxylamine, periodicacid, ammonium persulfate, other periodates, iodates,peroxomonosulfates, peroxymonosulfuric acid, perborates, malonamide,combinations of these, and the like, that will aid in the removal of thematerial may alternatively be utilized. For example, tungsten may bedeposited as part of a replacement gate process in which the replacementgate comprises tungsten, and a CMP process such as described herein maybe used to remove excess tungsten and/or planarize the tungsten. Otherreactants may be used in order to remove other materials. For example,in some embodiments in which the material is an oxide, the reactant maycomprise HNO₃, KOH, NH₄OH, or the like. For example, an oxide may bedeposited to form a shallow trench isolation (STI) region, aninter-layer dielectric (ILD) region, an inter-metal dielectric (IMD)region, or the like, and a CMP process such as described herein may beused to remove excess oxide and/or planarize the oxide.

The abrasive may be any suitable particulate that, in conjunction withthe polishing pad 103, aids in the polishing of the wafer 109. In someembodiments, the abrasive may comprise silica, aluminum oxide, ceriumoxide, polycrystalline diamond, polymer particles such aspolymethacrylate or polymethacryclic, combinations of these, or thelike.

The surfactant may be utilized to help disperse the reactant andabrasive within the slurry 113 and to prevent (or at least reduce) theabrasive from agglomerating during a CMP process. In some embodiments,the surfactant may include sodium salts of polyacrylic acid, potassiumoleate, sulfosuccinates, sulfosuccinate derivatives, sulfonated amines,sulfonated amides, sulfates of alcohols, alkylanyl sulfonates,carboxylated alcohols, alkylamino propionic acids, alkyliminodipropionicacids, potassium oleate, sulfosuccinates, sulfosuccinate derivatives,sulfates of alcohols, alkylanyl sulfonates, carboxylated alcohols,sulfonated amines, sulfonated amides, alkylamino propionic acids,alkyliminodipropionic acids, combinations of these, or the like.However, these embodiments are not intended to be limited to thesesurfactants, as any suitable surfactant may alternatively be utilized asthe surfactant.

The remainder of the slurry 113 may be a solvent that may be utilized tocombine the reactant, the abrasive, and/or the surfactant and allow themixture to be moved and dispersed onto the polishing pad 103. In someembodiments, the solvent of the slurry 113 may be a solvent such asdeionized (DI) water or an alcohol. However, any other suitable solventmay alternatively be utilized.

Referring to further to FIG. 1, in the illustrated embodiment, the CMPapparatus 100 has a single polisher head (such as the polisher head 105)and a single polishing pad (such as the polishing pad 103). However, inother embodiments, the CMP apparatus 100 may have multiple polisherheads and/or multiple polishing pads. In some embodiments in which theCMP apparatus 100 has multiple polisher heads and a single polishingpad, multiple wafers may be polished at the same time. In otherembodiments in which the CMP apparatus 100 has a single polisher headand multiple polishing pads, a CMP process may be a multi-step process.In such embodiments, a first polishing pad may be used for bulk materialremoval from a wafer, a second polishing pad may be used for globalplanarization of the wafer and a third polishing pad may be used to buffa surface of the wafer. In some embodiments, different slurries may beused for different CMP stages. In other embodiments, the same slurry maybe used for all CMP stages.

FIG. 2 illustrates a plan view of the CMP apparatus 100 in accordancewith some embodiments. In some embodiments, the polisher head 105 isconfigured to be rotated in a clockwise or a counter-clockwisedirection, as indicated by the double-headed arrow 102. In someembodiments, the polisher head 105 is configured to be translatedlaterally over the surface of the polishing pad 103, as indicated by thedouble-headed arrows 104. In some embodiments, the polisher head 105 maybe rotated and translated simultaneously.

FIGS. 3A-B illustrate side views of the CMP apparatus 100 in accordancewith some embodiments. In addition to the platen 101 and polisher head105 of the CMP apparatus (as shown in FIG. 1 and FIG. 2), FIG. 3A andFIG. 3B show a holder 150 in accordance with some embodiments. Theholder 150 holds the polisher head 105 and is used to place the polisherhead 105 onto the polishing pad 103 and also may be used to remove thepolisher head 105 from the polishing pad 103. FIG. 3A shows the holder150 when it is not holding the polisher head 105, and FIG. 3B shows theholder 150 when it is holding the polisher head 105. The CMP apparatus100 may include a holder positioning apparatus (not shown) that isattached to the holder 150 and is configured to raise, lower, translate,rotate, or otherwise position the holder 150.

The holder 150 includes catches 152 configured to fit within catch holes106 in the carrier 107 of the polisher head 105, as shown in FIG. 3B.The catches 152 are configured to be moved once within the catch holes106 such that the catches 152 are able to hold the polisher head 150.The respective step is illustrated as step 404 in the process flow 400shown in FIG. 9. In this manner, the holder 150 can place the polisherhead 105 onto the polishing pad 103 and then move the catches 152 torelease the polisher head 105 (as shown in FIG. 3A). The respectivesteps are illustrated as steps 406 and 408 in the process flow 400 shownin FIG. 9. In some embodiments, the wafer 109 is attached to the suctioncup 108 while the polisher head 150 is held by the holder 150. To removethe polisher head 105 from the polishing pad 103 (e.g., after the CMPprocess is completed), the holder 150 may align the catches 152 over thecatch holes 106, insert the catches 152 into the catch holes 106, andthen lift the polisher head 105 (as shown in FIG. 3B). The respectivesteps are illustrated as steps 416 and 418 in the process flow 400 shownin FIG. 9.

In this manner, the polisher head 105 may be placed on the polishing pad103 such that during a CMP process, the polisher head 105 is free tomove without being attached to another component of the CMP apparatus100. In some embodiments, the polisher head 105 is placed on thepolishing pad 103 and released by the holder 150 (e.g., by moving thecatches 152) prior to rotation of the polisher head 150 by the magneticfields generated by the stators 130, described in greater detail below.The holder 150 shown in FIG. 3 is an example, and in other embodiments,catches 152 and/or catch holes 106 may be more or fewer than shown inFIG. 1, 2, or 3A-B and may have other shapes or configurations.

Turning to FIG. 4, a magnetic base 110 and a platen 201 are shown, inaccordance with some embodiments. The magnetic base 110 and platen 201shown in FIG. 4 may be part of a CMP apparatus such as CMP apparatus 100shown in FIGS. 1 through 3A-B or CMP apparatus 200 shown in FIGS. 5A-B.For clarity, other components of the CMP apparatus are not shown in FIG.4. The magnetic base 110 may be part of a polisher head 105 similar tothose shown in FIGS. 1 through 3A-B, and the platen 201 may be similarto the platen 101 shown in FIGS. 1 through 3A-B.

The magnetic base 110 shown in FIG. 4 includes multiple magnets 120.FIG. 4 illustrates ten magnets 120, but more or fewer magnets 120 may bepresent in other embodiments. In some embodiments, the magnets 120 areevenly spaced around the perimeter of the magnetic base 110, as shown inFIG. 4, though the magnets 120 may have other arrangements in otherembodiments. In some embodiments, the magnets 120 are arranged such thatthe orientations of adjacent magnets 120 are parallel and have oppositepolarity. As an illustrative example, magnet 120A is oriented parallelto the axis of the magnetic base 110, with the north (“N”) pole of themagnet 120A toward the bottom of the magnetic base 110 and with thesouth (“S”) pole of the magnet 120A toward the top of the magnetic base110. The magnet 120B is adjacent the magnet 120A and parallel to theaxis of the magnetic base 110 (and thus is also parallel to the magnet120A), but the south pole of the magnet 120B is toward the bottom of themagnetic base 110 and the north pole of the magnet 120B is toward thetop of the magnetic base 110. The magnets 120 may be any suitablemagnets, such as permanent magnets (e.g., comprising Ferrite, NdFeB, orthe like), electromagnets (e.g., comprising copper wiring around a coreor the like), superconducting magnets (e.g., NbTi, (RE)BCO, or thelike), other types of magnets, the like, or a combination.

The platen 201 shown in FIG. 4 is similar to the platen 101 shown inFIGS. 1 through 3B, except the platen 201 includes multiple stators 130.The stators 130 are controllable magnets (e.g., electromagnets or thelike) disposed within the platen 201. In some embodiments, the stators130 are stationary with respect to the polisher head 105 during a CMPprocess, and in some embodiments, the platen 101 and/or the stators 130rotate during a CMP process. The stators 130 are configured to generatemagnetic fields that interact with the magnetic fields of the magnets120 of the magnetic base 110 in order to move the polisher head 105(described in greater detail below). FIG. 4 illustrates eight stators130, but more or fewer stators 130 may be present in other embodiments.The number of stators 130 within the platen 201 may be the same as ordifferent than the number of magnets 120 in the polisher head 105 of theCMP apparatus 100. In some embodiments, the stators 130 are evenlyspaced around the perimeter of the platen 201, as shown in FIG. 4,though the stators 130 may have other arrangements in other embodiments.The stators 130 may be oriented parallel to the axis of the platen 201or parallel to the top surface of the platen 201, or a combination.

In some embodiments, each of the stators 130 within the platen 201 areconnected to a controller 132. The controller 132 is configured tocontrol each stator 130 to control its magnetic field strength and/orpolarity. For example, the controller 132 can control the electricalpower supplied to a stator 130 to increase or decrease the strength ofthe magnetic fields generated by that stator 130. For example, to beginthe CMP process, the controller 132 can provide power to the stators 130in order to generate magnetic fields using the stators 130. Therespective step is illustrated as step 410 in the process flow 400 shownin FIG. 9. In some embodiments, the controller 132 may send signals to astator 130 that instruct the stator 130 to adjust its magnetic fieldstrength and/or polarity. In some embodiments, a stator 130 may generatea magnetic field having between about 100 Gauss and about 20,000 Gauss,though other magnetic fields are possible. In some cases, generating astronger magnetic field may allow for a greater pressure to be exertedbetween the wafer 109 and the polishing pad 103. In this manner, stators130 that are configured to generate a larger range of magnetic fieldstrengths can allow for more flexibility and control of the polishingpressures used during a CMP process. In some embodiments, the controller132 can control the polarity of the electrical power (e.g., direction ofelectrical current or polarity of voltage) supplied to a stator 130 inorder to control the polarity of the magnetic fields generated by thatstator 130. For example, the controller 132 can control a stator 130 tohave either its north pole or its south pole oriented toward one end ofthe stator 130, and the controller 132 can control the stator 130 toreverse the polarity of the stator 130. In some cases, the polarity ofthe electrical power may be controlled to have a sinusoidal variation intime.

Turning to FIGS. 5A-5B, plan views of an example operation of a CMPapparatus 200 is shown, in accordance with some embodiments. The CMPapparatus 200 may be similar to the CMP apparatus 100 (see FIGS. 1through 3A-B). The CMP apparatus 200 includes a polisher head 105 thatincludes a magnetic base 110, which may be similar to the magnetic base110 described in FIG. 4. The CMP apparatus 200 also includes a platen201 similar to the platen 201 described in FIG. 4. FIGS. 5A-5B show thepolisher head 105 as placed on the polishing pad 103 (not shown in FIGS.5A-B) during a CMP process, similar to FIGS. 1 and 3A. In FIGS. 5A-5B,the poles of the magnets 120 closest to the platen 201 are labeled as“N” for north and “S” for south, and the poles of the stators 130closest to the polisher head 105 are also labeled. For example, as shownin FIGS. 5A-5B, the magnet 120A has its north pole oriented toward thebottom of the magnetic base 110, and the magnet 120B has its south poleoriented toward the bottom of the magnetic base 110, similar to magnet120A and magnet 120B shown in FIG. 4. The illustrations shown in FIGS.5A-5B are also reflected schematically in the process flow 400 shown inFIG. 9.

In FIGS. 5A-5B, the strength and polarity of the stators 130 arecontrolled (e.g., by controller 132) to translate and rotate thepolisher head 105 using the interaction (e.g., attraction or repulsion)between the magnetic fields of the stators 130 and the magnetic fieldsof the magnets 120. The strength and polarity of the stators 130 may becontrolled based on the position or orientation of the polisher head 105in order to move the polisher head 105. For example, in FIG. 5A, thepolarity of stator 130A is controlled such that the south pole of stator130A is oriented toward the top of the platen 201, and the polarity ofstator 130B is controlled such that the north pole of stator 130A isoriented toward the top of the platen 201.

After the polisher head 105 has been placed on the polishing pad 103 andreleased by the holder 150 (e.g., steps 404 and 406 in FIG. 9), thecontroller 132 may be used to control the magnetic fields of the stators130 to polish the wafer 109 by rotating and/or translating the polisherhead 105 on the polishing pad 103. The respective step is illustrated asstep 412 in the process flow 400 shown in FIG. 9. Because the polisherhead 105 is freestanding after being released by the holder 150, thepolisher head 105 may be rotated or translated on the polishing pad 103without limitations imposed by mechanical linkages, wires, tubes, etc.In some embodiments, to rotate the polisher head 105, the controller 132may repeatedly reverse the polarities of the stators 130. For example,the controller 132 may supply alternating currents to the stators 130,the alternating currents having appropriate frequencies to produce thedesired rotation. At the moment shown in FIG. 5A, the south pole ofstator 130A attracts the north pole of magnet 120A and repels the southpole of magnet 120B. The north pole of stator 130B also attracts thesouth pole of magnet 120B. Similarly, other stators 130 attract or repelcorresponding nearby magnets 120. This interaction between the magnets120 within the polisher head 105 and the stators 130 that surround thepolisher head 105 causes the polisher head 105 to rotate. Turning toFIG. 5B, the polisher head 105 has been rotated, and the controller 132has reversed the polarity of the stators 130. The controller 132reverses the polarity of the stators 130 to maintain the rotation of thepolisher head 105. For example, in FIG. 5B, the polarity of stator 130Ahas been reversed, and the north pole of stator 130A repels the northpole of magnet 130A. The polarity of stator 130B has been reversed, andthe south pole of stator 130B attracts the north pole of magnet 130A andrepels the south pole of magnet 120A. The polarity of the stators 130may be subsequently reversed to continue rotating the polisher head 105.In this manner, the polisher head 105 can be rotated during a CMPprocess.

In FIGS. 5A-5B, the polisher head 105 is rotated in a counter-clockwisedirection, but in other cases the polisher head 105 may be rotated in aclockwise direction or may maintain a fixed angular position. In someembodiments, the controller 132 may not reverse the polarity of all ofthe stators 130 simultaneously during a CMP process. In someembodiments, the controller 132 may activate or deactivate some stators130 during a CMP process to translate or rotate the polisher head 105.In some cases, the controller 132 may control the stators 130 toincrease or decrease the speed of rotation. The polisher head 105 may berotated about a fixed axis or may be rotated about a moving axis. Insome embodiments, the polisher head 105 may be rotated at a speedbetween about 0 RPM and about 1000 RPM. By controlling the rotationspeed, some characteristics of the CMP process may be controlled, suchas the material removal rate. Thus, the use of magnetic fields generatedby stators 130 as described can allow for greater flexibility anddynamic control of the CMP process. Additionally, FIGS. 5A-B illustratethe polisher head 105 as being off-centered from the platen 201, but inother cases the polisher head 105 may be maintained approximatelycentered on the platen 201.

In some embodiments, the controller 132 may reduce or cease powering thestators 130 to stop the polisher head 105 from moving. For example,after the wafer 109 has been sufficiently polished, the stators 130 maybe controlled in this manner to stop further polishing due to movementof the polisher head 105. The respective step is illustrated as step 414in the process flow 400 shown in FIG. 9. The holder 150 may then becontrolled to remove the polisher head 105 from the polishing pad 103 byaligning the catches 152 over the catch holes 106, inserting the catches152 into the catch holes 106, and then lifting the polisher head 105from the polishing pad 103. The respective steps are illustrated assteps 416 and 418 in the process flow 400 shown in FIG. 9. In someembodiments, the stators 103 may be controlled to position the polisherhead 105 at a particular location or orientation on the polishing pad103 to facilitate removal of the polisher head 105 by the holder 150.After removing the polisher head 105 from the polishing pad 103, thewafer 109 may be released from the suction cup 108. The respective stepis illustrated as step 420 in the process flow 400 shown in FIG. 9. Insome cases, the polisher head 105 may be released from the holder 150prior to releasing the wafer 109 from the suction cup 108.

In addition to the lateral forces that rotate the polisher head 105, theinteraction between the magnetic fields of the magnets 120 and themagnetic fields of the stators 130 to can be controlled to producevertical forces on the polisher head 105 that press the wafer 109 intothe polishing pad 103. For example, the controller 132 may control thestrength of the magnetic fields of the stators 130 such that thevertical component of the attractive forces between the magnets 120 andthe stators 130 are greater than the vertical component of the repulsiveforces between the magnets 120 and the stators 130. For example, thepolarity and strength of each stator 130 may be controlled to increasethe attractive forces exerted by stators 130 that are close to magnets120 of opposite polarity by increasing the strength of those stators'130 magnetic fields and to decrease the repulsive forces exerted bystators 130 that are close to magnets 120 of the same polarity bydecreasing the strength of those stators' 130 magnetic fields. In someembodiments, the stators 130 may be controlled to provide a pressure ofthe wafer 109 against the polishing pad 103 that is between about 0 psiand about 10 psi. By controlling the pressure, some characteristics ofthe CMP process may be controlled, such as the material removal rate.Thus, the use of magnetic fields generated by stators 130 as describedcan allow for greater flexibility and dynamic control of the CMPprocess.

In this manner, the interaction of the magnets 120 in the polisher head105 and the stators 130 in the platen 201 can be controlled to polishthe wafer 109 during a CMP process. By the use of magnets to move afreestanding polisher head 105 during a CMP process, there may be lesschance of mechanical or electrical failure than if the polisher head 105were moved by a mechanism during a CMP process. In some cases,maintenance costs may also be relatively lower. Additionally, themagnetic fields generated by the stators 130 can be controlled togenerate uniform pressure between the wafer 109 and the polishing pad103. In some cases, the wafer 109 can be maintained at a more parallelorientation with respect to the polishing pad 103, reducing unevenpolishing of the wafer 109.

Turning to FIG. 6, a CMP apparatus 300 is shown, in accordance with someembodiments. The CMP apparatus 300 may be similar to the CMP apparatus100 (see FIGS. 1 through 3A-3B) or CMP apparatus 200 (see FIGS. 5A-5B),except the CMP apparatus 300 includes stators 330 that are external tothe platen 101. The CMP apparatus 300 includes a polisher head 105 thatincludes a magnetic base 110, which may be similar to the magnetic base110 described in FIG. 4 or may be similar to the magnetic base 110described below in FIG. 7. FIG. 6 shows the polisher head 105 as placedon the polishing pad 103 during a CMP process, similar to FIGS. 1 and3A. The illustration shown in FIG. 6 is also reflected schematically inthe process flow 400 shown in FIG. 9.

Still referring to FIG. 6, the stators 330 are attached to the CMPapparatus 300 such that they are laterally separated from the polisherhead 105 and the platen 101. The stators 330 surround the polisher head105 and are configured to generate magnetic fields that interact withthe magnetic fields of the magnets 120 of the magnetic base 110 in orderto move the polisher head 105 (described in greater detail below). Insome embodiments, the stators 330 are stationary with respect to thepolisher head 105 during a CMP process. In some embodiments, each of thestators 330 are connected to a controller 132, which may be similar tothe controller 132 described previously in FIG. 4. The controller 132 isconfigured to control each stator 330 to control its magnetic fieldstrength and/or polarity. In some embodiments, the controller 132 maysend signals to a stator 330 that instruct the stator 330 to adjust itsmagnetic field strength and/or polarity. In some embodiments, a stator330 may generate a magnetic field having between about 100 Gauss andabout 20,000 Gauss. In some cases, generating a stronger magnetic fieldmay allow for a greater pressure to be exerted between the wafer 109 andthe polishing pad 103, or to increase the rotational/translationalforces exerted on the polishing head 105. In this manner, stators 330that are configured to generate a larger range of magnetic fieldstrengths can allow for more flexibility and control of the polishingpressures or polishing head 105 movement during a CMP process. In someembodiments, the controller 132 can control the polarity of theelectrical power (e.g., direction of electrical current or polarity ofvoltage) supplied to a stator 330 in order to control the polarity ofthe magnetic fields generated by that stator 330. For example, thecontroller 132 can control a stator 330 to have either its north pole orits south pole oriented toward one end of the stator 330, and thecontroller 132 can control the stator 330 to reverse the polarity of thestator 330.

In some embodiments, the stators 330 are configured to be repositionedin order to control the interaction between the magnetic fields of thestators 330 and the magnetic fields of the polisher head 105. Forexample, a stator 330 may be brought closer to the polisher head 105 toincrease the strength of the magnetic field of the stator 330 thatinteracts with the polisher head 105. As another example, a stator 330may be tilted to change the relative strengths of the horizontalcomponent and vertical component of the magnetic field of the stator 330that interacts with the polisher head 105. For example, the stators 330may be tilted to an angle between about 0 degrees and about 90 degreeswith respect to the plane of the platen 101. A more vertical angle(e.g., closer to 90 degrees) may impart a stronger vertical component ofthe magnetic field relative to the horizontal component, and a morehorizontal angle (e.g., closer to 0 degrees) may impart a strongerhorizontal component of the magnetic field relative to the verticalcomponent. By adjusting the location and/or tilt of the stators 330 inthis manner, the movement of the polisher head 105 may be controlledduring a CMP process.

In some embodiments, the repositioning of the stators 330 may becontrolled by the controller 132. For example, the controller 132 maysend signals to actuators (not shown) connected to the stators thattranslate and/or tilt the stators 330. In some embodiments, the stators330 may be repositioned collectively or repositioned separately. Forexample, different stators 330 may be positioned at the same relativeheight or tilt angle, or different stators may be positioned atdifferent relative heights or tilt angles. FIG. 6 shows examplerepositioning of the stators 330 to positions 332, though stators 330may be repositioned in other orientations or arrangements. In someembodiments, the positions of individual stators 330 may be adjustedduring a CMP process, for example, to impart a greater or lessermagnetic field on a particular region of the polisher head 105. In thismanner, the strength and/or position of the stators 330 may be adjustedduring a CMP process to maintain a more level polishing, for instance.

Turning to FIG. 7, a magnetic base 110 is shown, in accordance with someembodiments. The magnetic base 110 may be used as part of a polisherhead 105 such as that shown in FIG. 6 or 8. The magnetic base 110 issimilar to the magnetic base 110 shown in FIG. 4, except for thearrangement of the magnets 120. FIG. 7 illustrates eight magnets 120,but more or fewer magnets 120 may be present in other embodiments. Insome embodiments, the magnets 120 are evenly spaced in a single ringaround the perimeter of the magnetic base 110, as shown in FIG. 7,though the magnets 120 may have other arrangements or orientations inother embodiments. As shown in FIG. 7, the magnets 120 are arranged suchthat the magnets 120 are positioned end-to-end in a ring pattern. Themagnets 120 are arranged such that the adjacent poles of neighboringmagnets are opposite poles (e.g., the north pole of one magnet 120 isadjacent the south pole of a neighboring magnet 120). In this manner,the magnets 120 are arranged laterally within the magnetic base 110, inwhich all of the magnetic poles of the magnets 120 are approximatelycoplanar. The magnets 120 may be any suitable magnets, such as thosedescribed above in FIG. 4. The illustration shown in FIG. 7 is alsoreflected schematically in the process flow 400 shown in FIG. 9.

Turning to FIG. 8, a plan view of an example operation of a CMPapparatus 300 is shown, in accordance with some embodiments. FIG. 8shows the polisher head 105 as placed on the polishing pad 103 (notshown in FIG. 8) during a CMP process, similar to FIGS. 5A-B. FIG. 8illustrates eight stators 330 and a polisher head 105 having fourmagnets 120, but more or fewer stators 330 or magnets 120 may be presentin other embodiments. The number of stators 330 may be the same as ordifferent than the number of magnets 120 in the polisher head 105 of theCMP apparatus 300. FIG. 8 shows the stators 330 as evenly spaced in acircular arrangement surrounding the polisher head 105, but in otherembodiments, the stators 130 may not be evenly spaced or may not be in acircular arrangement. The illustration shown in FIG. 8 is also reflectedschematically in the process flow 400 shown in FIG. 9.

Referring to FIG. 8, the strength and polarity of the stators 330 arecontrolled (e.g., by controller 132) to translate and rotate thepolisher head 105 using the interaction (e.g., attraction or repulsion)between the magnetic fields of the stators 330 and the magnetic fieldsof the magnets 120. The movement of the polisher head 105 by the stators330 shown in FIG. 8 may be similar in operation to the movement of thepolisher head 105 by the stators 130 shown in FIGS. 5A-B. For example,at the moment shown in FIG. 8, the south pole of stator 330A attractsthe north pole of magnet 120C and repels the south pole of magnet 120D.The north pole of stator 330B also attracts the south pole of magnet120D and repels the north pole of magnet 120D. Similarly, other stators330 attract or repel corresponding nearby magnets 120. This interactionbetween the magnets 120 within the polisher head 105 and the stators 330that surround the polisher head 105 causes the polisher head 105 torotate. In some embodiments, to rotate the polisher head 105, thecontroller 132 may repeatedly reverse the polarities of the stators 330.

In FIG. 8, the polisher head 105 is rotated in a counter-clockwisedirection, but in other cases the polisher head 105 may be rotated in aclockwise direction or may maintain a fixed angular position. In someembodiments, the controller 132 may not reverse the polarity of all ofthe stators 330 simultaneously during a CMP process. In someembodiments, the controller 132 may activate or deactivate some stators330 during a CMP process to translate or rotate the polisher head 105.In some embodiments, the controller 132 may reposition the stators 330during a CMP process. In some cases, the controller 132 may control thestators 330 to increase or decrease the speed of rotation. The polisherhead 105 may be rotated about a fixed axis or may be rotated about amoving axis. In some embodiments, the polisher head 105 may be rotatedat a speed between about 0 RPM and about 1000 RPM. By controlling therotation speed, some characteristics of the CMP process may becontrolled, such as the material removal rate. Thus, the use of magneticfields generated by stators 330 as described can allow for greaterflexibility and dynamic control of the CMP process. Additionally, FIG. 8illustrates the polisher head 105 as being off-centered from the platen101, but in other cases the polisher head 105 may be maintainedapproximately centered on the platen 101. In some embodiments, theplaten 101 may be rotated (e.g. by a motor) during the CMP process.

Additionally, the interaction between the magnetic fields of the magnets120 and the magnetic fields of the stators 330 to can be controlled toproduce a vertical force on the polisher head 105 that presses the wafer109 into the polishing pad 103. For example, the controller 132 maycontrol the strength of the magnetic fields of the stators 330 or thepositions of the stators 330 such that the vertical component of therepulsive forces between the magnets 120 and the stators 330 are greaterthan the vertical component of the attractive forces between the magnets120 and the stators 330. For example, stators 330 that are closer tomagnets 120 of opposite polarity may have their magnetic strengthdecreased to decrease the attractive forces, and stators that are closerto magnets 120 of the same polarity may have their magnetic strengthincreased to increase the repulsive forces. In some embodiments, thecontroller 132 may control the vertical position, lateral position,radial position, or the tilt of the stators 330 in order to control thevertical force on the polisher head 105. In some embodiments, thestators 130 may be controlled to provide a pressure of the wafer 109against the polishing pad 103 that is between about 0 psi and about 10psi.

In some cases, the use of magnets to move a polisher head during a CMPprocess may allow for a more uniform polish. The magnetic interactioncan be controlled during the CMP process to both translate and rotatethe polisher head. Additionally, the pressure with which the polisherhead presses on the polishing pad may be controlled by controlling themagnetic interaction. In some cases, the polishing head may befreestanding and not connected to another component during a CMPprocess. A holder mechanism may be used to place the polisher head onthe polishing pad or remove the polisher head from the polishing pad. Insome cases, the polisher head may have no mechanical or electroniccomponents, for example, if the magnets used are permanent magnets, orif the wafer is held in place by a suction cup instead of an activelygenerated negative pressure. By using magnets to move the polisher head,the number of mechanical or electronic components (e.g., linkages,motors, tubing, bearings, wiring, etc.) in a CMP apparatus may bereduced. By using fewer such components, the likelihood of componentbreakdown may be reduced, and the cost of component maintenance may alsobe reduced. The weight or cost of a CMP apparatus may also be reduced.

In an embodiment, a method includes placing a polisher head on platen,the polisher head including a set of first magnets, and controlling aset of second magnets to rotate the polisher head on the platen, whereincontrolling the set of second magnets includes reversing the polarity ofat least one second magnet of the set of second magnets to produce amagnetic force on at least one first magnet of the set of first magnets,wherein the set of second magnets are external to the polisher head. Inan embodiment, the set of second magnets is disposed within the platen.In an embodiment, the set of second magnets is external to the platen.In an embodiment, controlling the set of second magnets further includesvertically translating at least one second magnet of the set of secondmagnets. In an embodiment, controlling the set of second magnetsincludes controlling the strength of the magnetic force generated by atleast one second magnet of the set of second magnets. In an embodiment,the magnetic force includes a downward force. In an embodiment, thepolisher head is placed on the platen by a polisher head holder, andwherein after placing the polisher head on the platen, the polisher headis detached from the polisher head holder. In an embodiment, thepolisher head is free of electrical connections to other components. Inan embodiment, controlling the set of second magnets includessimultaneously controlling the polarity of each second magnet of the setof second magnets. In an embodiment, the first magnets are orientedlaterally within the polisher head.

In an embodiment, a method includes attaching a wafer to a polisherhead, wherein the polisher head includes multiple first magnets, placingthe polisher head on a platen, wherein the platen includes multiplesecond magnets, wherein each second magnet includes an electromagnetcoupled to a controller, and using the controller, controlling theelectrical power delivered to each second magnet to generate magneticfields that impart lateral forces on the multiple first magnets torotate the polisher head with respect to the platen. In an embodiment,the multiple first magnets are oriented vertically within the polisherhead. In an embodiment, the method further includes controlling theelectrical power delivered to each second magnet to generate magneticfields that impart vertical forces on the multiple first magnets topress the wafer onto the platen. In an embodiment, the wafer is pressedonto the platen with a pressure between 0 psi and 10 psi. In anembodiment, the method further includes controlling the electrical powerdelivered to each second magnet to generate magnetic fields that impartlateral forces to laterally translate the polisher head. In anembodiment, the polisher head includes a suction cup, and whereinattaching the wafer to the polisher head includes using the suction cup.In an embodiment, after placing the polisher head on the platen, thepolisher head is free of mechanical connection to the platen.

In an embodiment, a polishing apparatus includes a polisher head, thepolisher head including multiple first magnets, a platen includingmultiple second magnets, a holder configured to place the polisher headon the platen, wherein the holder is configured to release the polisherhead after placing the polisher head on the platen, and a controllercoupled to the multiple second magnets, the controller configured tocontrol the polarity of each of the second magnets to rotate thepolisher head after the holder has released the polisher head. In anembodiment, the polisher head includes catch holes, and the holderincludes catch mechanisms configured to be inserted within the catchholes. In an embodiment, the first magnets include permanent magnets.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method, comprising: placing a polisher head ona platen, the polisher head comprising a set of first magnets; andcontrolling a set of second magnets to rotate the polisher head on theplaten, wherein controlling the set of second magnets comprisesreversing the polarity of at least one second magnet of the set ofsecond magnets to produce a magnetic force on at least one first magnetof the set of first magnets, wherein the set of second magnets areexternal to the polisher head.
 2. The method of claim 1, wherein the setof second magnets is disposed within the platen.
 3. The method of claim1, wherein the set of second magnets is external to the platen.
 4. Themethod of claim 1, wherein controlling the set of second magnets furthercomprises vertically translating at least one second magnet of the setof second magnets.
 5. The method of claim 1, wherein controlling the setof second magnets comprises controlling the strength of the magneticforce generated by at least one second magnet of the set of secondmagnets.
 6. The method of claim 1, wherein the magnetic force comprisesa downward force.
 7. The method of claim 1, wherein the polisher head isplaced on the platen by a polisher head holder, and wherein afterplacing the polisher head on the platen, the polisher head is detachedfrom the polisher head holder.
 8. The method of claim 1, wherein thepolisher head is free of electrical connections to other components. 9.The method of claim 1, wherein controlling the set of second magnetscomprises simultaneously controlling the polarity of each second magnetof the set of second magnets.
 10. The method of claim 1, wherein thefirst magnets are oriented laterally within the polisher head.
 11. Themethod of claim 1 further comprising attaching a wafer to the polisherhead prior to placing the polisher head on the platen.
 12. A method,comprising: attaching a wafer to a polisher head, wherein the polisherhead comprises a plurality of first magnets; placing the polisher headon a platen, wherein the platen comprises a plurality of second magnets,wherein each second magnet comprises an electromagnet coupled to acontroller; and using the controller, controlling the electrical powerdelivered to each second magnet to generate magnetic fields that impartlateral forces on the plurality of first magnets to rotate the polisherhead with respect to the platen.
 13. The method of claim 12, wherein theplurality of first magnets are oriented vertically within the polisherhead.
 14. The method of claim 12, further comprising controlling theelectrical power delivered to each second magnet to generate magneticfields that impart vertical forces on the plurality of first magnets topress the wafer onto the platen.
 15. The method of claim 14, wherein thewafer is pressed onto the platen with a pressure between 0 psi and 10psi.
 16. The method of claim 12, further comprising controlling theelectrical power delivered to each second magnet to generate magneticfields that impart lateral forces to laterally translate the polisherhead.
 17. The method of claim 12, wherein the polisher head comprises asuction cup, and wherein attaching the wafer to the polisher headcomprises using the suction cup.
 18. The method of claim 12, wherein,after placing the polisher head on the platen, the polisher head is freeof mechanical connection to the platen.
 19. A method, comprising:attaching a wafer to a polisher head, wherein the polisher headcomprises a plurality of first magnets; placing the polisher head on aplaten, wherein the platen comprises a plurality of second magnets,wherein each second magnet comprises an electromagnet coupled to acontroller; and using the controller, controlling the electrical powerdelivered to each second magnet to generate magnetic fields that impartlateral forces on the plurality of first magnets to rotate the polisherhead with respect to the platen, wherein controlling the electricalpower delivered to each second magnet comprises reversing the polarityof at least one second magnet of the set of second magnets to produce amagnetic force on at least one first magnet of the set of first magnets.20. The method of claim 19, wherein the plurality of first magnets arearranged horizontally along a circumference of the polisher head.